/**********************************************************************
 * SailmiPIM - modular cross-platform feature Personal Information Manager Tools.
 * Copyright(C) 2006-2014  Georg Rudoy
 *
 * Distributed under the Boost Software License, Version 1.0.
 *(See accompanying file LICENSE or copy at https://www.boost.org/LICENSE_1_0.txt)
 **********************************************************************/

#include "networkdiskcachegc.h"
#include <QTimer>
#include <QDir>
#include <QDirIterator>
#include <QtConcurrentRun>
#include <QDateTime>
#include <QtDebug>
#include <util/sll/qtutil.h>
#include <util/sll/prelude.h>
#include <util/sll/util.h>
#include <util/threads/futures.h>

namespace SailmiPIM::Util
{
	NetworkDiskCacheGC::NetworkDiskCacheGC()
	{
		const auto timer = new QTimer { this };
		connect(timer,
				&QTimer::timeout,
				this,
				&NetworkDiskCacheGC::HandleCollect);
		timer->start(60 * 60 * 1000);
	}

	NetworkDiskCacheGC& NetworkDiskCacheGC::Instance()
	{
		static NetworkDiskCacheGC gc;
		return gc;
	}

	namespace
	{
		struct SizeCollectInfo
		{
			QMultiMap<QDateTime, QString> Items_;
			qint64 TotalSize_ = 0;
		};

		SizeCollectInfo CollectSizes(const QString& cacheDirectory)
		{
			SizeCollectInfo result;

			const QDir::Filters filters = QDir::AllDirs | QDir:: Files | QDir::NoDotAndDotDot;
			QDirIterator it { cacheDirectory, filters, QDirIterator::Subdirectories };

			while(it.hasNext())
			{
				const auto& path = it.next();
				const auto& info = it.fileInfo();
				result.Items_.insert(info.birthTime(), path);
				result.TotalSize_ += info.size();
			}

			return result;
		}
	}

	QFuture<qint64> NetworkDiskCacheGC::GetCurrentSize(const QString& path) const
	{
		return QtConcurrent::run([path] { return CollectSizes(path).TotalSize_; });
	}

	Util::DefaultScopeGuard NetworkDiskCacheGC::RegisterDirectory(const QString& path,
			const std::function<int()>& sizeGetter)
	{
		auto& list = Directories_ [path];
		list.push_front(sizeGetter);
		const auto thisItem = list.begin();

		return Util::MakeScopeGuard([this, path, thisItem] { UnregisterDirectory(path, thisItem); }).EraseType();
	}

	void NetworkDiskCacheGC::UnregisterDirectory(const QString& path, CacheSizeGetters_t::iterator pos)
	{
		if(!Directories_.contains(path))
		{
			qWarning() << Q_FUNC_INFO
					<< "unknown directory"
					<< path;
			return;
		}

		auto& list = Directories_ [path];
		list.erase(pos);

		if(!list.empty())
			return;

		Directories_.remove(path);
		LastSizes_.remove(path);
	}

	namespace
	{
		qint64 Collector(const QString& cacheDirectory, qint64 goal)
		{
			if(cacheDirectory.isEmpty())
				return 0;

			qDebug() << Q_FUNC_INFO << "running..." << cacheDirectory << goal;

			auto sizeInfoResult = CollectSizes(cacheDirectory);

			for(auto i = sizeInfoResult.Items_.constBegin();
					i != sizeInfoResult.Items_.constEnd() && sizeInfoResult.TotalSize_ > goal;
					++i)
			{
				QFile file { *i };
				sizeInfoResult.TotalSize_ -= file.size();
				file.remove();
			}

			qDebug() << "collector finished" << sizeInfoResult.TotalSize_;

			return sizeInfoResult.TotalSize_;
		}
	};

	void NetworkDiskCacheGC::HandleCollect()
	{
		if(IsCollecting_)
		{
			qWarning() << Q_FUNC_INFO
					<< "already collecting";
			return;
		}

		QList<QPair<QString, int>> dirs;
		for(const auto& pair : Util::Stlize(Directories_))
		{
			const auto& getters = pair.second;
			const auto minSize =(*std::min_element(getters.begin(), getters.end(),
						Util::ComparingBy(Apply)))();
			dirs.append({ pair.first, minSize });
		}

		if(dirs.isEmpty())
			return;

		IsCollecting_ = true;

		Util::Sequence(this,
				QtConcurrent::run([dirs]
						{
							QMap<QString, qint64> sizes;
							for(const auto& pair : dirs)
								sizes [pair.first] = Collector(pair.first, pair.second);
							return sizes;
						})) >>
				[this](const QMap<QString, qint64>& sizes)
				{
					IsCollecting_ = false;
					for(const auto& pair : Util::Stlize(sizes))
						LastSizes_ [pair.first] = pair.second;
				};
	}
}
